The applications cross-referenced above disclose, inter alia, the making of carbon monoxide-containing ethylene interpolymers, and their use as HF-heatable polymers. As disclosed there, these CO-containing polymers can be blended with other polymers to impart HF-heatability to the whole. The interpolymers can be ethylene/carbon monoxide or ethylene/other monomer/carbon monoxide (e.g. E/AA/CO and the like) containing up to about 40, preferably about 5 to about 30, weight percent CO. The polymers are preferably prepared by interpolymerizing a mixture of the monomers in a stirred autoclave at elevated temperature and pressure, using a free radical initiator, thereby producing random interpolymers (often called "random copolymers" even when more than 2 monomers are used).
U.S. Pat. No. 2,495,292 discloses the preparation of an E/CO copolymer containing 40 mol % of CO and also the hydrogenation of the CO groups to COH groups.
The following listed patents are believed to be representative of the art pertaining to interpolymers of carbon monoxide and monoolefins:
U.S. Pat. No. 2,495,286; U.S. Pat. No. 2,497,323; U.S. Pat. No. 2,641,590; PA1 U.S. Pat. No. 3,083,184; U.S. Pat. No. 3,248,359; U.S. Pat. No. 3,530,109; PA1 U.S. Pat. No. 3,676,401; U.S. Pat. No. 3,689,460; U.S. Pat. No. 3,694,412; PA1 U.S. Pat. No. 3,780,140; U.S. Pat. No. 3,835,123; U.S. Pat. No. 3,929,727; PA1 U.S. Pat. No. 3,948,832; U.S. Pat. No. 3,948,873; U.S. Pat. No. 3,948,850; PA1 U.S. Pat. No. 3,968,082; U.S. Pat. No. 3,984,388; U.S. Pat. No. 4,024,104; PA1 U.S. Pat. No. 4,024,325; U.S. Pat. No. 4,024,326; U.S. Pat. No. 4,139,522; PA1 U.S. Pat. No. 4,143,096; and U.S. Pat. No. 4,304,887.
U.S. Pat. No. 4,137,382 and U.S. Pat. No. 4,172,939 disclose ethylene/vinyl acetate/carbon monoxide terpolymers.
It is well-known in the relevant art that polyvinyl alcohol (PVOH) is prepared by hydrolyzing polyvinyl esters, usually polyvinyl acetate (PVA), and that ethylene/vinyl alcohol (EVOH) copolymers are prepared by hydrolyzing copolymers of ethylene/vinyl esters, usually ethylene/vinyl acetate (EVA) copolymers. Some references disclose that complete hydrolysis of all the vinyl acetate (or ester) groups is quite difficult, thus one may find a small residual or trace amount of acetate (or ester) groups remaining along the polymer chain, even in commercially available vinyl alcohol polymers.
It is also disclosed in the art that polyvinyl alcohol and ethylene/vinyl alcohol copolymers (both being referred to in places herein as "VOH-containing polymers" or as "vinyl alcohol polymers") are highly resistant to oxygen transport, thus are good barriers for oxygen. Generally the oxygen barrier properties are considerably reduced in inverse proportion to increasing humidity, but are increased in direct proportion to the amount of vinyl alcohol groups in the polymer chain or in indirect proportion to the amount of ethylene groups present.
It has now been found that a blend comprising a vinyl alcohol polymer and a carbon monoxide-containing ethylene copolymer has very good oxygen barrier properties at low humidity and which retains a surprising and beneficial amount of the good oxygen barrier properties in high humidity. We have also found that the processability of the vinyl alcohol polymer is substantially improved by the addition of the CO-containing ethylene polymer. Furthermore the HF-heatability of the blend is a beneficial feature.